OPERABLE AGGREGATES PROPERTY TO MINIMIZE CEMENT QUANTITY IN PORTLAND CEMENT CONCRETE

Aggregate shape, texture, and grading have a significant effect on the performance of fresh concrete. Aggregate blends with well-shaped, rounded, and smooth particles require less paste for a given slump than blends with flat, elongated, angular, and rough particles. At the same time, uniform grading with proper amounts of each size result in aggregate blends with high packing and in concrete with low water demand. Optimized Aggregate blends have high packing, requiring low amounts of paste. As a result, they are less expensive and will have less durability problems caused by the paste such as heat generation, porosity, and drying shrinkage. Current C 33 standard limits the amount of material passing the N 200 sieve (micro fines) to 7 percent. However, manufactured fine aggregate (MFA) usually has between 10 and 20 percent micro fines. These limits, intended for natural sands, force MFA producers to wash aggregate incrementing costs and generating environmental issues. Research at The University of Texas and experience in other countries show that good quality concrete can be made with MFA with high-micro fines content.